The present invention is directed to a method for optimizing an automatic amplifier setting in radio receivers, particularly mobile radio receivers in a cellular mobile radio telephone network having base stations in a mutual spatial arrangement.
In traditional radio-frequency receivers, amplifiers having one or more variable amplifier stages, known as Automatic Gain Control (AGC) are realized for compensating chronologically fluctuating received powers.
A severe problem of fluctuating received power occurs in the field of mobile radio telephone services. Moreover, transmission power regulating is utilized in mobile radio telephone services for efficiently maintaining the transmission quality. The convergence of these facts makes the design of the automatic gain control extraordinarily difficult. The additional active variation of the transmission power added to the fluctuating transmission power leads to a situation that can only be very conditionally governed by the receiver.
Traditional AGC loops employ only past reception levels for defining future AGC values. For example, the AGC is set to an average value of the reception level of the last measurement interval, for example in the last second. The block circuit diagram of FIG. 1 shows such an arrangement wherein two radio communication stations communicating with one another experience chronologically changing transmission losses. Every radio communication station contains a receiver E having an automatic gain control AGC and a transmitter S having an adaptive power control APC. There is a logical linkage (entered in broken lines) between the two APC controls.
Remaining fluctuations must be covered by an adequately liberal design of the range of dynamics of the reception stages. Given currently standard digital receivers, this means that the analog-to-digital converter must be designed with an adequately large word width in order, on the one hand, to reliably avoid over modulation and, on the other hand, to still assure adequately good resolution of the signal.